Standard metal organic chemical vapor deposition (MOCVD) processing consists of post deposition in-situ treatments of thermally deposited metal films having a predetermined thickness via plasma or hydrogen (H2) thermal bake to purify the thermally deposited metal films of predetermined thickness. Total film thickness of the thermally deposited metal films is achieved by varying the number of deposition and post-deposition treatment cycles, as determined by the dimensions of the structural features on semiconductor substrates. Standard MOCVD processing leads to deposition of rough cobalt (Co) film filled inside the features. The rough cobalt (Co) film pinches off early in the deposition process resulting in significant seam formation within the feature. Once the entry path into the feature is sealed no additional cobalt (Co) atoms can be transported into the seam during deposition. Therefore, a limited number of cobalt (Co) atoms can migrate into the feature during densification via high temperature hydrogen (H2) anneal. The distance for cobalt (Co) atoms to transport down to the lower portion of the feature becomes too large. As a result, voids are formed within the feature. While increasing the treatment frequency can reduce the number of voids, increasing the treatment frequency also reduces productivity significantly. Increasing the precursor flow enhances filling atoms inside the feature, but still cannot achieve a void free fill without sacrificing productivity.
Accordingly, the inventors have developed improved techniques to deposit void free cobalt in features disposed in a substrate.